1. Field of the Invention
The present invention relates to a car curtain folded by rolling up, particularly to a curtain for the rear window of a car being driven by a threaded rod engaging with nuts, with springs serving as an auxiliary drive for unfolding and attenuating too fast winding up of the curtain.
2. Description of Related Art
As shown in FIGS. 11 and 12, rear window car curtains currently used in Mercedes and Opel cars each comprise: a base 10, fixed on a car body; a winding device 15, mounted on the base 10 and having a main shaft 16, a curtain 17, and a leading rod 18; a driving device 20, mounted on the base 10 and having an output shaft 21 and a connecting piece 22; left and right driving rods 25, 26, having primary ends which are respectively connected with two opposite ends of the connecting piece 22; left and right connecting rods 30, each roughly shaped like the letter L with a center that is hingedly connected with the base 10, a relatively short endpiece 31 at a lower end which is connected with one of the left and right driving rods 25, 26 and a relatively long extension part 32 with an upper end that is glidingly connected with the leading rod 18. By above assembly, when the driving device 20 is operated, the connecting piece 22 turns in a direction indicated by arrows F, taking along the connecting rods 30, so that the endpieces 31 thereof are pulled inward, as indicated by arrows F, and the extension parts 32 turn upward, pulling the leading rod 18 upward and thus unfolding the curtain 17.
This type of car curtain is easy to operate, but has the following shortcomings.    1. During unfolding of the curtain, an uppermost position is reached only slowly or not at all.    2. During rolling up of the curtain, the curtain drops rapidly.    3. Rapid dropping of the curtain impairs stability of the mechanism.    4. Excessive forces on the mechanism cause gears to break.